1. Field of the Invention
The present invention relates to a coating film removal method for removing at least a portion of a coating film from a coated member, in which the coating film is formed over a substrate of the coated member, and more particularly to a method for removing a carbon-based coating film containing carbon as a main component. The present invention also relates to a method for regenerating a coated member, which removes a coating film from the coated member, and then forms a new coating film over the member.
2. Description of the Related Art
Generally, a coating film meeting a desired performance is formed over the surfaces of tools, molds, or elements of various devices. For example, a hard film is formed over the surface of a tool or mold requiring durability. As such a tool or mold is used, the hard film is damaged. In this case, the hard film is completely removed from the surface of the tool or mold, and a new hard film is formed over the tool or mold surface, to enable re-use of the tool or mold. Also, it may be desired to remove the hard film from a disadvantage region where the hard film exists. If the hard film has a thickness larger than a desired thickness, it may also be necessary to remove the surface portion of the hard film, in order to adjust the dimension of the hard film.
An example of a method for removing a hard film is a chemical treatment. For example, Japanese Laid-open Patent Publication No. H5-112885 discloses a removing agent which comprises a mixed aqueous solution comprising an alkali hydroxide as a main component, to be usable for removal of a titanium coating film or a coating film of a titanium compound such as TiN, TiC, or TiCN. Japanese Laid-open Patent Publication No. H8-325755 discloses a method for stripping a hard film of TiAlN, using an aqueous solution of pH 10 or more containing permanganate ions and/or bichromate ions.
However, it is difficult to remove a carbon-based coating film such as an amorphous carbon (diamond-like carbon (DLC)) film, using the above-mentioned chemical treatment. This is because such a carbon-based coating film is chemically stable. In the case of Japanese Laid-open Patent Publication No. 2003-200350, abrasive particles are injected, together with air, onto a DLC film of a tool, in which the DLC film is formed on the surface of a substrate of the tool, in order to remove the DLC film from the tool. The case of Japanese Laid-open Patent Publication No. 2003-200350 has a fear that, due to the use of the abrasive, the surface roughness of the substrate may increase after the removal of the DLC film, or even the substrate may be abraded, thereby causing a deformation in the dimension of the tool.
Also, Japanese Laid-open Patent Publication No. H5-339758 discloses a method for etching a DLC film in a glow discharge or arc discharge atmosphere. Carbon, which is a main component of the DLC film, can be easily removed as it is burned during a reaction with activated oxygen. However, where the DLC film contains silicon or metal elements, it is difficult to remove the DLC film. Furthermore, the method requires high costs because it is necessary to use an apparatus for generating glow discharge or arc discharge.